What are the origins of the commercial minus sign (⁒)?

Question

While reading the Wikipedia article about the Plus and minus signs I found the so called commercial minus sign (Unicode character U+2052 and HTML symbol ⁒). It looks similar to an Obelus (÷) or Percent sign (%) as you can see:

After some more research and googling for the German term "kaufmännisches Minuszeichen" I found that the commercial minus sign was and is widely used in bookkeeping to indicate a minus sign such as the following example shows. (It was also common to write ./. on typewriters instead.)

100€ "deducting" 20% equals 80€

The problem is that I can’t find any good information about this symbol and its history. As @El Otmani Ali pointed out in his post one theory is that this symbol is a "quicker / cursive based variant of the division sign in some old German books" (see his answer and this mailing list on unicode.org). On the other hand why should we use a different symbol, when we want to set a character italic?

So, do you know the origins of this rarely used and not really documented sign?

^{Note: The sans-serif typeface DejaVu Sans was used in the examples.}

Answer 1

Based on an answer in this thread, this minus sign was used in bookkeeping, because the - was already in use.

After all the amounts were put in, they were checked twice. When the amount was correct, one would mark it by putting a little horizontal bar behind it. The bar meant the amount was correct.

Since the usual minus sign could be confusing and leading someone to believe an amount was checked when it wasn't, a different minus sign was used, the Commercial minus sign

Here is an example:

    100,00 -
+   100,00 -
./. 100,00 -
----------
    100,00 -

Answer 2

I did not know about it before, but after some good research, it seems like it is just an quicker/cursive based variant of the division sign in some old German books. These are just speculations based on one of the Unicode.com mailing list discussions, the mails are pretty interesting so I'd invite you to take a look to this e-mail and the 5 next answers, it will hopefully give you more insight.

The book that's refered to in the e-mail conversation can be found on Google Books here. (it's in German)

Answer 3

Let me answer @elegant's question. I don't have enough reputation to answer there, so let me answer here:

Context

In the answer by @Pie Bie, Pie Bie says that people used the horizontal line symbol to mean they had already double-checked a value, so they needed to find a different symbol. If you're in accounting you really don't want it to look like you had checked a value when in fact you hadn't.

@elegent asked why people used the "-" to mean "double checking" if many other symbols were avaiable.

My hypothesis

We do a similar thing in Brazil, and in fact I thought this might be common. Given how we move the pen to create this horizontal line, I'd say it evolved from a check mark (✓). Let me explain the hypothesis.

To start doing check marks, you touch the pen in the paper, do a small downwards movement and then an upwards movement, both being kind of diagonal. But double checking in accounting is a LOT of repetitive work; people get tired and lose fine motor control, and so they start doing less and less of the downward movement. But the less they go downwards, the less they can go upwards, because it would increasingly start looking like a forward slash ("/"), which is already a division sign and would also create confusion.

And so now they're pressing the pen against the paper, making what's essentially a dot, with only the "intention" of doing the initial downwards movement. I mean, they didn't just start consciously doing a clear, objective, straight horizontal movement: after all, they don't want it to look like a minus sign. I made a drawing of how that would look like. (Pardon the quality, but I just wanted to emulate a tired person writing.)

So your check marks start becoming worse, this actually happened to me when grading tests. Of course, I didn't "come up" with it, I based it off seeing my teachers in middle/high school who did the same, and it was common enough it happened automatically and I just assumed my students in uni would understand (I mean, I wouldn't let it get this bad if I thought it would be unrecognizable). Heh, I do remember one teacher in high school doing it in a way that was impossible to distinguish from the ／, which they used for wrong.

Anyway, I suppose that to someone doing accounting on their own, the degradation of the check mark didn't matter, because they were only marking to themselves anyway. But if someone else is checking down the road, or, maybe your office grows and it's multiple people, it starts causing confusion, especially because most people would never let their check mark degrade so much.

Well, I hope I helped, even though the question is kind of old I doubt anyone would stumble over this explanation.